Preoperative muscle health can predict distinct recovery patterns of patient-reported outcomes during 1 year after knee arthroplasty.

BACKGROUND/AIMS: Although knee arthroplasty (KA) generally improves physical function, the postoperative recovery process exhibits significant inter-individual heterogeneity. It remains unclear whether preoperative muscle health indicators can predict distinct longitudinal recovery trajectories. The main objective of this study was to examine whether preoperative muscle mass, quadriceps strength, and phase angle (PhA) of the operated limb can predict functional recovery patterns over 12 months following KA. A secondary objective was to identify distinct longitudinal trajectories of postoperative functional recovery using patient-reported outcomes.

METHODS: This was a prospective cohort study conducted at single center in Kobe, Japan. Eligible participants were patients with knee osteoarthritis scheduled to undergo primary unicompartmental or total knee arthroplasty. Functional outcome was assessed using the functional activities subscale of the Knee Society Scoring System (KSS) at preoperatively and 3, 6, and 12 months postoperatively. The skeletal muscle mass index (SMI), quadriceps strength, and PhA of the operated limb were measured as muscle health indicators at preoperatively. Group-based trajectory modeling (GBTM) was applied to identify the trajectories of the KSS functional activities score. Using multinomial logistic regression model, we investigated whether SMI, quadriceps strength, and PhA on the operated limb could predict membership of the trajectories of KSS functional activities score.

RESULTS: A total of 1056 patients were included in the main analysis. The mean age was 72.3 years, 78.3% were women, 68% of patients underwent TKA. The GBTM identified four trajectory groups as follows: Group 1 (low start, moderate improvement), Group 2 (low start, high improvement), Group 3 (medium start, moderate improvement), and Group 4 (high start, moderate improvement). The multinomial logistic regression model showed that patients with stronger quadriceps strength and higher PhA were less likely to belong to Groups 1, 2, or 3 than to Group 4. The RRRs (95% CI) per 1 standard deviation (SD) increase in quadriceps strength, relative to Group 4, were 0.42 (0.36-0.66) for Group 1, 0.69 (0.54-0.88) for Group 2, and 0.84 (0.70-1.03) for Group 3. The corresponding RRRs (95% CI) per 1 SD increase in PhA were 0.52 (0.39-0.68) for Group 1, 0.65 (0.51-0.83) for Group 2, and 0.80 (0.66-0.96) for Group 3. In contrast, a weak association was observed between SMI and trajectory membership. The RRRs (95%CI) per 1 SD increase in SMI were 0.89 (0.61-1.29) for Group 1, 0.84 (0.58-1.20) for Group 2, and 1.01 (0.77-1.32) for Group 3.

CONCLUSION: These findings suggest that assessing preoperative muscle strength and quality enables to predict the high risk of poor functional recovery after knee arthroplasty. It has important clinical implications for optimizing perioperative management and facilitating the setting of goals between clinicians and patients.